This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.
The ability to perform neutron spectroscopy offers significant benefits especially when using tensioned metastable fluid detectors (TMFDs) which offer unique advantages relative to state of art systems.
It is well-known that neutron detection with spectroscopy is of significant importance in a wide range of fields ranging from fundamental physics to nuclear power to combatting nuclear terrorism. Tension Metastable Fluid Detector (TMFD) technology offers a unique alternative to conventional neutron detectors for a wide array of applications. Highlights of TMFD capabilities include but are not limited to: high intrinsic efficiency for both fast and thermal neutrons, on-off times on the order of microseconds to allow phase locking with pulsed interrogation sources for active interrogation, gamma blindness to vastly decrease nuisance (interfering) background and allow active photon interrogation, single system directionality capabilities, the ability to extend to alpha and fission product detection, promising capability to perform neuron multiplicity assessments, the ability to change sensitivity on demand, and potentially with significant reduced cost and complexity of operation when compared to the state of the art.
Despite strong performance as a detector, usefulness of TMFDs in dose measurements or spectrometry requires knowledge of the response function to relate the tension state of the detector with the amount of energy deposited (by incoming radiation over nanometer scales) to the propensity to generate a Cavitation Detection Event (CDE). This constituted a key piece of information which, until now has remained intractable to assess with any reasonable level of accuracy. The mainstay elegantly simple so-called Thermal Spike Theory (TST) which robustly predicts CDEs for thermally superheated metastable fluids for bubble chambers fails, when applied to tensioned (room temperature) metastable fluids to describe the manifestation of CDEs. As vividly seen from Table 1, TST predicts energy barriers to nucleation of cavities in tensioned metastable state fluids that are more than an order of magnitude smaller than the barrier encountered experimentally.
TABLE 1Predicted (thermal-spike-theory) and actual TMFDexperimental energy barrier for detecting 210Po alpharecoils in acetone (at 20° C. and Pneg = −8.3 bar).Energy Barrier ComponentsEnergy (keV)Surface (Tension) energy5.7Expansion work (pdV)3.9Evaporation energy2Kinetic energy given to liquid0Viscous energy loss2.1Total predicted energy barrier13.7Actual ion recoil energy [3]101
As a result, applying TST to predict outcomes from TMFD experiments results in far more predicted CDEs than actually observed experimentally. Without the ability to model detector response for CDEs with reasonable accuracy for neutrons of different energies, it therefore, has remained unrealized to develop response matrices and to distinguish a large flux of particles with a small interaction cross-section from a small flux of particles with a large cross-section. While response curves for any arbitrary neutron source in a given source-detector geometry can be obtained experimentally and used to estimate the intrinsic TMFD detection efficiency, the spectral identification of an arbitrary neutron source in an arbitrary geometry requires rigorous knowledge of the TMFD's response function.
There is, therefore an unmet need for a novel approach to identify a response function to relate the tension state of the detector with the amount of energy deposited (by incoming radiation over nanometer scales) to the propensity to generate a CDE.